Technical Field
The present disclosure relates to a technology for detecting an object based on an image captured by a camera. In particular, the present disclosure relates to a technology that is mounted to a vehicle and used thereby.
Related Art
A moving object recognition system is conventionally known. In the system, a moving object in the periphery of a vehicle is recognized. A driver is then issued an alert or automatic braking of the vehicle is performed (referred to, hereafter, as simply “notification”). A distance from an own vehicle to the moving object can be directly measured using a distance sensor, such as a millimeter wave radar. Alternatively, the distance can be measured by image processing being performed using a stereo camera. A moving direction of the moving object and a relative speed of the moving object in relation to the own vehicle can be determined through analysis of measured distances arranged in chronological order. As a result of the moving direction of the moving object and the relative speed thereof in relation to the own vehicle being determined, a likelihood (degree of risk) of the moving object colliding with the own vehicle can be determined. Notification can be given based on the degree of risk.
In addition, as a simple and low-cost moving object recognition system, a system is also known in which a moving object is recognized by a single-lens camera that only includes a single optical system and an image sensor. Atypical method by which moving object recognition using a camera image is performed is a method in which image recognition is performed by the camera image being matched to a vehicle image (teacher data) stored in advance. As another method, a method focusing on movement of feature points (optical flow) in a plurality of images that are continuous in terms of time is also known (Japanese Patent Publication No. 4919036 and JP-A-2014-29604).
The method in which a vehicle is recognized through image recognition requires, in advance, a large volume of teacher data related to vehicles to be detected. In addition, even should a large volume of teacher data be prepared, a problem arises in that vehicles having unique shapes differing from those of ordinary vehicles cannot be detected. In addition, in the invention focusing on optical flow, described in Japanese Patent Publication No. 4919036 and JP-A-2014-29604, although objects moving in a lateral direction are easily detected, objects moving along a direction from the own vehicle towards a vanishing point of the camera image are sometimes may be difficult to detect, due to characteristics of the images captured by the camera.